Sensitive sprinkler

ABSTRACT

A sensitive sprinkler includes a body having an inlet port coupled to a fluid supply line and an outlet orifice having a deflector mounted adjacent thereto to deflect fluid flowing through said sprinkler. A rupture disc valve is positioned in the fluid flow path between the inlet port and outlet orifice to block fluid flow through the flow path. An explosive squib is mounted in the fluid flow path upstream of the rupture disc so that when exploded an expansive gas directs a pressure through said fluid to rupture the disc. A fire detector assembly electrically activates the squib substantially immediately upon detection of a fire.

United States Patent [191 Allard et 1 SENSITIVE SPRINKLER [73] Assignee: International Telephone and Telegraph Corporation, Nutley, NJ. [22] Filed: Feb. 28, 1973 [21] Appl. No.: 336,849

[52] US. Cl 169/28, 169/37 [51] Int. Cl. A62c 35/08 [58] Field of Search 169/28, 37, 42; 340/228.1; 337/373 [56] References Cited UNITED STATES PATENTS 2,713,624 7/1955 Kagan 337/373 X 2,742,094 4/1956 Mathisen 169/28 2,766,832 10/1956 Mathisen 169/28 X 2,795,282 6/1957 Mathisen 169/28 X 2,981,939 4/1961 Carbauh 340/228.1 3,284,002 11/1966 Edelman et a1 337/373 X i. "i if 70 28 52 3Q 1'38 50 1 I 4o 3 2e [111 3,834,463 [451 Sept. 10, 1974 3,515,217 6/1970 Jamison 169/28 X 3,604,511 9/1971 Griffith et a1. 169/28 3,726,344 4/1973 Rothman et a1. 169/37 [57] ABSTRACT A sensitive sprinkler includes a body having an inlet port coupled to a fluid supply line and an outlet orifice having a deflector mounted adjacent thereto to deflect fluid flowing through said sprinkler. A rupture disc valve is positioned in the fluid flow path between the inlet port and outlet orifice to block fluid flow through the flow path. An explosive squib is mounted in the fluid flow path upstream of the rupture disc so that when exploded an expansive gas directs a pressure through said fluid to rupture the disc. A fire detector assembly electrically activates the squib substantially immediately upon detection of a fire.

17 Claims, 5 Drawing Figures .11 i.- f F 76 I A f 707E 'asnscro/z SENSITIVE SPRINKLER BACKGROUND OF THE INVENTION In automatic sprinkler systems for extinguishing fires, it is important that the sprinkler system be sensitive so as to respond rapidly to a fire. Many automatic sprinkler systems include a valve support and releasing device that includes parts that are held together by solder. At a predetermined temperature, the solder melts and the valve supports separate releasing the water. Such systems may be too slow under certain conditions. The sprinklers are typically mounted in a ceiling which may be remote from a fire in the same enclosure. Consequently extensive damage to persons or property may be done before such automatic sprinkler systems turn OBJECTS OF THE INVENTION It is an object of this invention to provide a new and improved sprinkler.

It is another object of this invention to provide an improved sprinkler that is extremely sensitive to detection of fires to release fluid.

It is a further object of this invention to provide a sensitive sprinkler including a fire detector assembly that may be mounted remote from the sprinkler but electrically coupled thereto and close to a possible fire locatIon.

SUMMARY OF THE INVENTION A sensitive sprinkler includes an inlet port and an outlet orifice and having a body that defines a fluid flow path between the inlet port and the outlet orifice. A rupture disc valve is positioned in said fluid flow path between the inlet port and outlet orifice to block fluid flow through the flow path. An explosive squib is mounted in said fluid flow path upstream of the rupture disc for providing an expansive gas upon activation to direct pressure against the rupture disc through the fluid to rupture the disc. A detector assembly for detecting a fire and electrically activate the squib is provided to insure extreme sensitivity in responding to fires.

BRIEF DESCRIPTION OF THE DRAWINGS The novel features that are considered to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, both as to organization and method of operation, as well as advantages thereof, will best be understood by referring to the accompanying drawings and the following description in which:

FIG. 1 is a sectional view of a sensitive sprinkler embodying the present invention and in which the sprinkler is shown in an of position;

FIG. 2 is a bottom view of the sensitive sprinkler shown in FIG. 1;

FIG. 3 is a broken sectional view of a portion of the sprinkler shown in FIG. 1 taken along section line 3-3;

FIG. 4 is a schematic circuit diagram of the fire detector assembly incorporated into the sprinkler of FIG. 1; and

FIG. 5 is a sectional front view illustrating another embodiment of the invention.

DETAILED DESCRIPTION Referring to FIG. 1, a sensitive sprinkler 10, which is shown in a pendant position, includes a body 12 having an inlet port 14 that is threaded so as to be connected to a source of pressurized fluid (not shown). The sprinkler body 12 may for example be formed by a casting of a suitable material, such as bronze. The sprinkler body 12 also includes an outlet portion having a tapering aperture formed centrally therein to define an outlet orifice or nozzle 18 for said sprinkler. The outlet orifice portion 18 is threaded so as to be mated to the threaded open end of the sprinkler body 12 so as to secure the outlet portion 18 to the sprinkler body 12. Mounted adjacent the orifice 18 is a deflector 20. The deflector 20, which may be of a conventional type, as shown in FIG. 2, is spaced from the orifice 18 and positioned perpendicular to the projected axis of fluid flow passage by a yoke 22. The deflector 20 is secured to the yoke by means of a rivet 24. The yoke, which is generally U-shaped, is in turn fastened onto the orifice member 18 by a force fit.

Positioned upstream of the orifice 18 is a rupture disc valve 26. The rupture disc 26 may, for example, comprise a stainless steel disc, an aluminum disc or a cop per disc or any other suitable type disc. The rupture disc is positioned into intimate contact with a bearing surface 28 on the sprinkler body 12 by means of a retaining ring 30. The outlet orifice member 18 holds the retaining ring 30 pressed against the rupture disc 26 so as to block any fluid flow through a fluid flow path.

The fluid flow path is defined by the inlet port 14, the outlet nozzle 18 as well as a forked intermediate section 31. As shown in FIG. 3, the intermediate section includes branches 32 and 33 that separate and then join together again. in front of the rupture disc 26.

An explosive squib 34 is mounted directly in the fluid flow path and at the axial center thereof in a housing 36. The squib 34 is held in the housing 36 by means of an annular retainer screw. The squib 34 is an explosive device that produces an expanding gas when activated. The expanding gas is directed to rupture the disc 26 by means of a directional opening 38 in the housing 36. The expanding gas may also be used to operate a latch andhence open a valve rather than rupture a disc.

A fire detector assembly 40 is mounted on a flange 42. The flange 42 is held onto the sprinkler body by" means of screws 43, as shown in FIG. 2. The fire detector assembly 40 includes a mercury switch or thermostat 46 that is protected by a guard 48. The mercury switch 46 is mounted in the flange 42 adjacent a circuit board 50 that contains other components of the fire detector assembly 40. Also mounted onthe flange 42 is a lens 44 which may be used to direct light on a solar cell array 48. The fire detector assembly 40 is coupled to activate the squib 34 via electrically conductive wires 52 that penetrate through the aperture in the retainer screw 37 to the squib 34. This configuration permits the easy replacement and servicing of the squib 34, the disc 26, and the detector 40 but of course these also may be a single unit.

A schematic circuit diagram of the fire detector assembly 40, which includes the components on the circuit board 50, is shown in FIG. 4. The fire detector assembly 40 includes a battery or first energy source 56 having its positive potential terminal coupled through a resistor 58 and a first unilateral conducting diode 60 to one plate of a capacitor 62. The diode 60 is poled to permit the battery 56 to charge the capacitor 62 through the resistor 58. A second energy source comprising the solar cell array 48 is coupled via a second unilateral conducting diode 66 to the capacitor 62. The diodes 60 and 66 are poled in opposition to each other with the aforementioned plate of the capacitor 62 coupled to the junction of the cathode of these diodes. The other plate of the capacitor 62 is coupled to the junction of the negative terminal of the battery 56 and the solar cell array 48. The capacitor 62 is electrically coupled directly across the series combination of the ther mostat 46 and the squib 34. The thermostat 46 includes mercury 47 that expands to cause the terminal 70 to make electrical contact with the terminal 72 and thereby cause the capacitor 62 to discharge through the mercury in the thermostat 46 to cause the squib 34 to tire.

In addition to the tire detector assembly 40, another fire detector 74 is shown in FIG. 1. The detector 74 is located remote from the sprinkler l and is coupled to fire the squib 34 by means of electrical conductors 76. The detector 74 may, for example, be located on the wall of an enclosure or near any potentially hazardous location. Thus the detector 74 can respond rapidly to a tire and transmit the response electrically to fire the explosive squib 34. The detector 74 may, for example, comprise a heat sensitive thermostatic switch similar to the thermostat 46. Alternatively, the detector 74 may be comprised of a smoke detector, or other type of detectors such as ionization or photoelectric. Furthermore, the detector 74 may comprise all three or more or any combination thereof if desired. The detector 74 may be utilized along with the thermostat 46 or in place of this thermostat. The operational status of the electrical components of both the sprinkler and the detectors are capable of being monitored.

OPERATION The sensitive sprinkler I0 is mounted in an enclosure, such as a room, in the ceiling. The local detector assembly 40 is mounted on the sprinkler l0 and additionally a detector 74 may be located remote from the sprinkler 10. Water from a pressurized source enters the inlet port 14 and fills the fluid flow path of the sprinkler but the rupture disc valve 26 prevents the water from flowing through the sprinkler 10. The capacitor 62, in the schematic diagram of FIG. 4, charges up to the higher potential of either-the battery 56 or the solar cell array 48. The battery 56 and the solar cell array 48 are isolated from each other due to the isolating effects of the diodes 60 and 66, which are poled in opposite directions to each other. When a predetermined heat is detected by the thermostat 46, the mercury 47 therein expands to cause the mercury to bridge the open circuit gap between the terminals 70 and 72. When this occurs, the capacitor 62 is connected across the squib 34. The capacitor 62 therefore discharges into the squib 34 and causes the squib 34 to explode. In the explosion, the squib 34 produces an expanding gas which is directed by the opening 38 in the squib housing 36 toward the rupture disc valve 26. The incomprcssibility of the water between the squib 34 and the rupture disc 26 transfers the force produced by the expanding gas to the rupture disc 26 and the disc 26 ruptures. The rupturing of the disc 26 opens the fluid flow path from the inlet port 14 to the orifice l8 and water flows to put out the tire.

The thermostat 46 is extremely sensitive to heat increases and this response is transmitted rapidly by the electrical conductors 52. The explosion produced by the electrical conductors 52 in the squib 34 to rupture the disc valve 26 is also an extremely rapid response to the detection of a tire by the sensitive sprinkler 10. Thus extreme sensitivity is provided by a sprinkler 10 embodying the invention.

It is to be noted that the inclusion of the two energy sources, namely, the battery 56 and the solar cell array 48, provide a backup to tire the squib 34. Thus, as the battery 56 ages and lowers the voltage to which the ow pacitor 62 would be charged, the solar cell array 48 effectively charges the capacitor 62 to maintain optimum operating conditions in the fire detector assembly.

ANOTHER EMBODIMENT OF THE INVENTION In FIG. 5, there is shown another embodiment of the invention. In this embodiment of the invention detector assembly attachment is attached to a sprinkler 82 that is already installed in a building. Thus existing sprinklers may be made sensitive by the use of the attachment 80. The sprinkler 82 may, for example, be a pendant sprinkler of the solder type. Such a sprinkler is of the fusible link type and includes a threaded inlet port 84 that is attached to a source of pressurized fluid (not shown). A fluid flow path in the body 85 of the sprinkler 82 is blocked by a button disc 86. The disc 86 is held in place by a strut 88 that is mounted between a book 90 and the disc 86. The hook 90 is held under tension by connecting the other end thereof to a bell shaped key 92 that is soldered to a bell shaped heat collector 94.

The detector assembly attachment 80 includes a bracket arm 96 that includes a clamp 98 that attaches to the body 85 of the sprinkler 82. The clamp 98 is pivotally connected together at one end and includes a pair of eye holes 100 and 102 at the other end. One of the eye holes 100 is threaded and a bolt 104 is inserted through the eye hole 102 to be screwed into the eye hole 100 to securely fasten the attachment 80 to the sprinkler 82.

A fire detector portion of the attachment 80 includes an explosive squib 106 that is positioned opposite the collector 94. A thermostat 108 that is protected by a guard 110 detects heat to cause the squib 106 to fire. The tire detector portion of the attachment 80 may, for example, be similar to that shown in FIGS. 1 and 4 and consequently will not be described in detail.

When the thermostat 108 detects heat produced by a tire, the squib 106 is fired and the explosion therein causes a molten slag to impinge on the collector 94. The molten slag melts the solder holding the key 92 to the collector 94 and the two members separate. The hook 90 is released from tension and the strut 88 falls away from the button disc. The fluid flow path through the sprinkler 82 is therefore opened and fluid flows to put out the tire.

It is to be noted that the explosive squib 106 ejects a molten slag rather than an expanding gas. The molten slag will adhere to any surface, but the bell shape of the collector 94 is efficient in collecting the heat from the molten slag. Thus the attachment 80 renders existing sprinklers sensitive and replacement of existing sprinklers is not necessary.

Thus in accordance with the invention, a sensitive sprinkler is provided. A sprinkler may either be rendered sensitive by including an attachment thereto or the sprinkler may be a unitary structure.

While the principles of the invention have been described in connection with specific structure it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of our invention as set forth in the objects thereof and in the accompanying claims.

We claim:

1. A sensitive sprinkler for a fire protection system and adapted to be coupled to a pressurized fluid supply line, comprising in combination:

a sprinkler body having an inlet adapted for coupling to said fluid supply line and an outlet for providing fluid, said sprinkler body defining a fluid flow path between said inlet and said outlet;

a deflector mounted adjacent said outlet to deflect and distribute fluid from said outlet;

means providing a rupture disc valve positioned in said fluid flow path between said inlet and said outlet to block fluid flow through said flow path;

a housing positioned upstream from the rupture disc valve and extending across the axis of the valve;

a directional opening formed in said housing and directed downstream towards the rupture disc valve;

an explosive squib mounted in said housing for providing an expansive gas upon activation which gas is directed through said directional opening to exert pressure against said rupture disc valve through the fluid upon explosion whereby the disc valve is ruptured; and

means providing a detector assembly for detecting a fire and for electrically activating said squib substantially immediately upon detection of a fire so as to provide extreme sensitivity in responding to fires by said sprinkler.

2. The combination in accordance with claim 1 wherein said detector assembly is positioned remote from said sprinkler.

3. The combination in accordance with claim 1 wherein said detector assembly comprises a heat sensitive mercury switch that expands upon detection of heat to close an electrical circuit to explode said squib.

4. The combination in accordance with claim I wherein said detector assembly comprises a smoke detector for detecting smoke due to a fire.

5. The combination in accordance with claim 1 wherein said detector assembly comprises an ionization detector for detecting ions produced by a flame due to a fire.

6. The combination in accordance with claim 1 wherein said housing is mounted in said fluid flow path and said fluid flow path defines a dual path that divides so that fluid flows around each side of said housing before joining together again before said rupture disc.

7. A sensitive sprinkler as described in claim 1, wherein said detector assembly comprises:

an electrical circuit including a battery coupled via a first unidirectional conducting diode to charge a 6 capacitor and solar cell coupled serially with a second unidirectional conducting diode which is poled to oppose the current flow through said first diode and that further includes a capacitor mounted between the junction of the said diodes and the junctions of said battery and said solar cell to receive a charge from both said battery and said solar cell with one of said devices being a standby for the other; and

a heat sensitive switch connecting said squib to said capacitor, whereby the switch closes at a predetermined temperature and the capacitor is discharged through the squib causing the squib to be activated.

8. An assembly attachment for a sprinkler having a fusible link, which attachment renders said sprinkler sensitive in response to fires comprising in combination:

an explosive squib mounted on said attachment for providing a molten slag when activated;

means for mounting said attachment on said sprinkler so that said squib directs said molten slag onto said fusible link when activated; and

fire detecting meanselectrically coupled to activate said squib upon detection of a fire.

9. An assembly attachment as described in claim 8, wherein said fire detecting means is mounted on said attachment and is self-powered.

10. An assembly attachment as described in claim 8, wherein said fire detecting means includes:

an electronic circuit including a self-contained power source and a capacitor connected to be charged by said power source; and

means for connecting said explosive squib to said ca pacitor in response to detection of a fire so that the capacitor is discharged through the explosive squib causing the explosive squib to be detonated.

11. An assembly attachment as described in claim 8,

wherein said fire detecting means comprises:

an electrical circuit including a battery coupled via a first unidirectional conducting diode to charge a capacitor and solar cell coupled serially with a second unidirectional conducting diode which is poled to oppose the current flow through said first diode and that further includes a capacitor mounted between the junction of the said diodes and the junctions of said battery and said solar cell to receive a charge from both said battery and said solar cell with one of said devices being a standby for the other; and switch means for connecting said squib to said capacitor in response to a fire, whereby the switch closes at a predetermined temperature and the capacitor is discharged through the squib causing the squib to be detonated. 12. A sensitive sprinkler for a fire protection system adapted to be coupled to a pressurized fluid supply line, comprising:

a sprinkler body having an inlet adapted for coupling to said fluid supply line and an outlet for providing fluid, said sprinkler body defining a fluid flow path between said inlet and said outlet;

a deflector mounted adjacent said outlet to deflect and distribute fluid from said outlet;

means providing a rupture disc valve positioned in said fluid flow path between said inlet and said outlet to block fluid flow through said flow path;

an explosive squib mounted in said fluid flow path upstream of said rupture disc for providing an expansive gas upon activation to direct pressure against said rupture disc through said fluid upon explosion to rupture said disc;

an electrical circuit including a battery coupled via a first unidirectional conducting diode to charge a capacitor and solar cell coupled serially with a second unidirectional conducting diode which is poled to oppose the current flow through said first diode and that further includes a capacitor mounted between the junction of the said diodes and the junctions of said battery and said solar cell to receive a charge from both said battery and said solar cell with one of said devices being a standby for the other; and

a heat sensitive switch connecting said squib to said capacitor, whereby the switch closes at a predetermined temperature and the capacitor is discharged through the squib causing the squib to be detonated.

13. A sensitive sprinkler for a fire protection system adapted to be coupled to a pressurized fluid supply line, comprising:

a sprinkler body having an inlet adapted for coupling to said fluid supply line and an outlet for providing fluid, said sprinkler body defining a fluid flow path between said inlet and outlet;

deflector means mounted adjacent said outlet for defleeting and distributing fluid from said outlet;

means for blocking the flow of fluid through said sprinkler body; electrically actuated explosive means for opening said blocking means;

an electronic circuit including a self-contained power source and a capacitor connected to be charged by said power source; and

fire detecting means for connecting said explosive means to said capacitor in response to detection of a fire so that the capacitor is discharged through the explosive means causing the explosive means to be detonated and the blocking means immediately opened upon the detection of a tire thereby providing a sprinkler having extreme sensitivity for rapidly extinguishing a fire.

14. A sensitive sprinkler as described in claim 13, wherein the self-contained power source comprises a battery and a solar cell each connected to charge the capacitor and provide a standby power source for the other.

15. A sensitive sprinkler for a tire protection system as described in claim 13, wherein the electronic circuit includes:

a battery coupled via a first unidirectional conducting diode to charge a capacitor and solar cell coupled serially with a second unidirectional conducting diode which is poled to oppose the current flow through said first diode and that further includes a capacitor mounted between the junction of the said diodes and the junctions of said battery and said solar cell to receive a charge from both said battery and said solar cell with one of said devices being a standby for the other.

16. A sensitive sprinkler for a fire protection system as described in claim 13, wherein the blocking means includes a fusible element and the explosive means is spaced from the blocking means and positioned to direct a molten slag onto the fusible element which adheres to the fusible element and causes it to rapidly melt.

17. A sensitive sprinkler for a fire protection system as described in claim 13, wherein the blocking means includes a rupturable disc valve and the explosive means is disposed within a housing positioned within the fluid and across the axis of the disc valve said housing having an opening directed towards the rupturable disc valve to direct the force of the explosive means towards the disc valve. 

1. A sensitive sprinkler for a fire protection system and adapted to be coupled to a pressurized fluid supply line, comprising in combination: a sprinkler body having an inlet adapted for coupling to said fluid supply line and an outlet for providing fluid, said sprinkler body defining a fluid flow path between said inlet and said outlet; a deflector mounted adjacent said outlet to deflect and distribute fluid from said outlet; means providing a rupture disc valve positioned in said fluid flow path between said inlet and said outlet to block fluid flow through said flow path; a housing positioned upstream from the rupture disc valve and extending across the axis of the valve; a directional opening formed in said housing and directed downstream towards the rupture disc valve; an explosive squib mounted in said housing for providing an expansive gas upon activation which gas is directed through said directional opening to exert pressure against said rupture disc valve through the fluid upon explosion whereby the disc valve is ruptured; and means providing a detector assembly for detecting a fire and for electrically activating said squib substantially immediately upon detection of a fire so as to provide extreme sensitivity in responding to fires by said sprinkler.
 2. The combination in accordance with claim 1 wherein said detector assembly is positioned remote from said sprinkler.
 3. The combination in accordance with claim 1 wherein said detector assembly comprises a heat sensitive mercury switch that expands upon detection of heat to close an electrical circuit to explode said squib.
 4. The combination in accordance with claim 1 wherein said detector assembly comprises a smoke detector for detecting smoke due to a fire.
 5. The combination in accordance with claim 1 wherein said detector assembly comprises an ionization detector for detecting ions produced by a flame due to a fire.
 6. The combination in accordance with claim 1 wherein said housing is mounted in said fluid flow path and said fluid flow path defines a dual path that divides so that fluid flows around each side of said housing before joining together again before said rupture disc.
 7. A sensitive sprinkler as described in claim 1, wherein said detector assembly comprises: an electrical circuit including a battery coupled via a first unidirectional conducting diode to charge a capacitor and solar cell coupled serially with a second unidirectional conducting diode which is poled to oppose the current flow through said first diode and that further includes a capacitor mounted between the junction of the said diodes and the junctions of said battery and said solar cell to receive a charge from both said battery and said solar cell with one of said devices being a standby for the other; and a heat sensitive switch connecting said squib to said capacitor, whereby the switch closes at a predetermined temperature and the capacitor is discharged through the squib causing the squib to be activated.
 8. An assembly attachment for a sprinkler having a fusible link, which attachment renders said sprinkler sensitive in response to fires comprising in combination: an explosive squib mounted on said attachment for providing a molten slag when activated; means for mounting said attachment on said sprinkler so that said squib directs said molten slag onto said fusible link when activated; and fire detecting means electrically coupled to activate said squib upon detection of a fire.
 9. An assembly attachment as described in claim 8, wherein said fire detecting means is mounted on said attachment and is self-powered.
 10. An assembly attachment as described in claim 8, wherein said fire detecting means includes: an electronic circuit including a self-contained power source and a capacitor connected to be charged by said power source; and means for connecting said explosive squib to said capacitor in response to detection of a fire so that the capacitor is discharged through the explosive squib causing the explosive squib to be detonated.
 11. An assembly attachment as described in claim 8, wherein said fire detecting means comprises: an electrical circuit including a battery coupled via a first unidirectional conducting diode to charge a capacitor and solar cell coupled serially with a second unidirectional conducting diode which is poled to oppose the current flow through said first diode and that further includes a capacitor mounted between the junction of the said diodes and the junctions of said battery and said solar cell to receive a charge from both said battery and said solar cell with one of said devices being a standby for the other; and switch meAns for connecting said squib to said capacitor in response to a fire, whereby the switch closes at a predetermined temperature and the capacitor is discharged through the squib causing the squib to be detonated.
 12. A sensitive sprinkler for a fire protection system adapted to be coupled to a pressurized fluid supply line, comprising: a sprinkler body having an inlet adapted for coupling to said fluid supply line and an outlet for providing fluid, said sprinkler body defining a fluid flow path between said inlet and said outlet; a deflector mounted adjacent said outlet to deflect and distribute fluid from said outlet; means providing a rupture disc valve positioned in said fluid flow path between said inlet and said outlet to block fluid flow through said flow path; an explosive squib mounted in said fluid flow path upstream of said rupture disc for providing an expansive gas upon activation to direct pressure against said rupture disc through said fluid upon explosion to rupture said disc; an electrical circuit including a battery coupled via a first unidirectional conducting diode to charge a capacitor and solar cell coupled serially with a second unidirectional conducting diode which is poled to oppose the current flow through said first diode and that further includes a capacitor mounted between the junction of the said diodes and the junctions of said battery and said solar cell to receive a charge from both said battery and said solar cell with one of said devices being a standby for the other; and a heat sensitive switch connecting said squib to said capacitor, whereby the switch closes at a predetermined temperature and the capacitor is discharged through the squib causing the squib to be detonated.
 13. A sensitive sprinkler for a fire protection system adapted to be coupled to a pressurized fluid supply line, comprising: a sprinkler body having an inlet adapted for coupling to said fluid supply line and an outlet for providing fluid, said sprinkler body defining a fluid flow path between said inlet and outlet; deflector means mounted adjacent said outlet for deflecting and distributing fluid from said outlet; means for blocking the flow of fluid through said sprinkler body; electrically actuated explosive means for opening said blocking means; an electronic circuit including a self-contained power source and a capacitor connected to be charged by said power source; and fire detecting means for connecting said explosive means to said capacitor in response to detection of a fire so that the capacitor is discharged through the explosive means causing the explosive means to be detonated and the blocking means immediately opened upon the detection of a fire thereby providing a sprinkler having extreme sensitivity for rapidly extinguishing a fire.
 14. A sensitive sprinkler as described in claim 13, wherein the self-contained power source comprises a battery and a solar cell each connected to charge the capacitor and provide a standby power source for the other.
 15. A sensitive sprinkler for a fire protection system as described in claim 13, wherein the electronic circuit includes: a battery coupled via a first unidirectional conducting diode to charge a capacitor and solar cell coupled serially with a second unidirectional conducting diode which is poled to oppose the current flow through said first diode and that further includes a capacitor mounted between the junction of the said diodes and the junctions of said battery and said solar cell to receive a charge from both said battery and said solar cell with one of said devices being a standby for the other.
 16. A sensitive sprinkler for a fire protection system as described in claim 13, wherein the blocking means includes a fusible element and the explosive means is spaced from the blocking means and positioned to direct a molten slag onto the fusible element which adheres to the fusible element and causes it to rapidly melt.
 17. A sensiTive sprinkler for a fire protection system as described in claim 13, wherein the blocking means includes a rupturable disc valve and the explosive means is disposed within a housing positioned within the fluid and across the axis of the disc valve said housing having an opening directed towards the rupturable disc valve to direct the force of the explosive means towards the disc valve. 